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authorAlex Deucher <alexander.deucher@amd.com>2013-09-27 18:09:54 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-04 10:57:34 -0800
commit78c3ae2cb101bc10f3b9cc851e826484246088e1 (patch)
treeef3b2c39e5dfcca4cbf19983d0d509cb0bab3b92 /drivers
parentb18cd40e6228da53f2781f37f9b94a1930c6ee9c (diff)
drm/radeon: use 64-bit math to calculate CTS values for audio (v2)
commit 062c2e4363451d49ef840232fe65e8bff0dde2a5 upstream. Avoid losing precision. See bug: https://bugs.freedesktop.org/show_bug.cgi?id=69675 v2: fix math as per Anssi's comments. Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpu/drm/radeon/r600_hdmi.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/gpu/drm/radeon/r600_hdmi.c b/drivers/gpu/drm/radeon/r600_hdmi.c
index 0efe2a93ca9..322e42737ef 100644
--- a/drivers/gpu/drm/radeon/r600_hdmi.c
+++ b/drivers/gpu/drm/radeon/r600_hdmi.c
@@ -75,8 +75,15 @@ static const struct radeon_hdmi_acr r600_hdmi_predefined_acr[] = {
*/
static void r600_hdmi_calc_cts(uint32_t clock, int *CTS, int N, int freq)
{
- if (*CTS == 0)
- *CTS = clock * N / (128 * freq) * 1000;
+ u64 n;
+ u32 d;
+
+ if (*CTS == 0) {
+ n = (u64)clock * (u64)N * 1000ULL;
+ d = 128 * freq;
+ do_div(n, d);
+ *CTS = n;
+ }
DRM_DEBUG("Using ACR timing N=%d CTS=%d for frequency %d\n",
N, *CTS, freq);
}